1. Field of the Invention
This invention relates to monitoring of flow conduits, such as a gas pipelines, and more particularly to an articulated mobile sensing and interrogation device for measuring parameters of interest of the flow conduit and remotely interrogating sensors attached to the pipeline.
2. Description of the Related Art
Fluid conduits such as pipelines and aqueducts extend for tens, hundreds, or thousands of kilometers and may be used to transport liquids, gases, slurries or combinations thereof. Such conduits may have multiple sections that run above or below ground. Sections may be run underground to avoid natural obstacles such as rivers or simply as a safety precaution. Other sections may be run above ground depending on the topography and underlying strata. Sensing stations are commonly located at major features, such as pumping station that may be separated by tens or hundreds of kilometers. Sensors are used to determine any of a number of parameters of interest related to the operation and safety of the conduit and/or related to the fluid transported therein. However, due to the relatively large separation of these stations, conditions that may be indicative of potential problems or failures may go undetected until they become so great as to cause a catastrophic event, such as for example a substantial leak that may be a serious environmental problem. It would be highly desirable to be able to determine various parameters relating to the physical condition of the conduit including, but not limited to, mechanical strain and stress, crack initiation and propagation, temperature, acceleration and vibration, seismic events, corrosion, pressure integrity, and flowing fluid properties, such as chemical species, radiation, and chemical contamination. The very nature of the length and location of such conduits, however, make the distribution of power and signal lines to multiple measurement stations substantially impractical and cost prohibitive.
Mobile devices, commonly called pigs, may be moved through a pipeline by the fluid pressure within the pipeline to provide information regarding the condition of the pipeline. The device can perform any number of tasks that can vary between simple tasks, such as cleaning pipelines, to more sophisticated tasks such as measurement of metal loss of the pipe due to corrosion, cracks, deformation and the like. Pigs that perform these tasks are called “smart pigs”. Smart pigs may consist of various modules, in which one of the modules commonly performs the function of propelling the smart pig through the pipeline. Such devices can have on-board devices for sensing a limited range of parameters of interest about the pipeline as the mobile device passes through the pipeline. Typically such devices detect parameters related to wear and corrosion, such as pipe diameter and/or magnetic flux leakage (MFL). Actual in situ physical parameters of the pipeline, such as those described previously, require sensors physically attached to the pipeline. Such sensors should preferably be self-contained such that they do not require electrical connections via cables. An example of such self-contained sensors is disclosed in U.S. patent application Ser. No. 10/421,475 filed on Apr. 23, 2003, previously incorporated herein by reference. Other parameters and tests may also be required to be carried out by the mobile device.
There is a demonstrated need, therefore, for a mobile device capable of performing tests along a pipeline as well as interrogating remote sensors attached to the pipeline.